Comparison of structural and chemical properties of black and red human hair melanosomes

Melanosomes in black and red human hair are isolated and characterized by various chemical and physical techniques. Different yields of 4-amino-hydroxyphenolanaline by HI hydrolysis (a marker for pheomelanin) and pyrrole-2,3,5-tricarboxylic acid by KMnO(4)/H(+) oxidation (a marker for eumelanin) indicate that the melanosomes in black hair are eumelanosomes, whereas those in red hair are mainly pheomelanosomes. Atomic force microscopy reveals that eumelanosomes and pheomelanosomes have ellipsoidal and spherical shapes, respectively. Eumelanosomes maintain structural integrity upon extraction from the keratin matrix, whereas pheomelanosomes tend to fall apart. The black-hair eumelanosomes have an average of 14.6 +/- 0.5% amino acids content, which is attributed to the internal proteins entrapped in the melanosomes granules. The red-hair melanosomes contain more than 44% of amino acid content even after extensive proteolytic digestion. This high content of amino acids and the poorly reserved integrity of red-hair melanosomes suggest that some proteins are possibly covalently bonded with the melanin constituents in addition to those that are entrapped inside the melanin species. Soluene solubilization assay indicates the absorbance of melanin per gram of sample, adjusted for the amino acid content, is a factor of 2.9 greater for the black-hair melanosomes than the red-hair melanosomes. Metal analysis reveals significant amounts of diverse heavy metal ions bound to the two types of melanosomes. The amount of Cu(II) and Zn(II) are similar but Fe(III) content is four times higher in the red-hair melanosomes. (13)C solid-state nuclear magnetic resonance spectra and infrared spectra are presented and are shown to be powerful techniques for discerning differences in the amino acid contents, the 5,6-dihydroxyindole-2-carboxylic acid:5,6-dihydroxyindole ratio, and the degree of cross-linking in the pigment. Excellent agreement is observed between these spectral results and the chemical degradation data.     

Palladium-catalyzed addition of arylboronic acids to aldehydes

[reaction: see text] Arylboronic acids react with aldehydes in the presence of a base and a catalytic amount of a palladium(0) complex with chloroform, affording the corresponding secondary alcohols in good yields. General palladium complexes have no catalytic activity without chloroform. Chloroform is essential for this reaction, and palladium complex that was prepared from Pd(PPh3)4 with CHCl3 showed good catalytic acitivity as well.     

1,3-Diphosphapropenes for novel chemistry of metal complexes

2-Methyl-3,3-diphenyl-1-(2,4,6-tri-t-butylphenyl)-1,3-diphosphapropene was obtained as a chelate ligand for palladium(II) and platinum(II) complexes. Sulfurization of 2-methyl-1,3-diphosphapropene mainly gave 3-thioxo-1,3-diphosphapropene which bears a PC-PS skeleton and was used as a ligand of transition-metal complexes. A doubly-sulfurized product of the 1,3-diphosphapropene, 1,3-dithioxo-1,3-diphosphapropene, was isolated and characterized. The palladium(II) complexes containing the ligated 1,3-diphosphapropenes were used for catalytic reactions such as cross-couplings and direct conversion of allyl alcohol to allylaniline.     

Potential nootropic agents, 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives

A series of 4-alkoxy-2-(1-piperazinyl)quinazoline derivatives was synthesized and evaluated for its ability to reverse a scopolamine-induced learned impairment in a one-trial passive avoidance task (antiamnestic activity). 2-(4-Allyl-1-piperazinyl)-4-pentyloxyquinazoline (4) showed more potent antiamnestic activity than such reference compounds as aniracetam, idebenone and bifemelane at a wide dose range (1-30 mg/kg]. Compound 4 also exhibited potent anticonvulsive and antihypoxic activities, and was selected as the most promising nootropic candidate agent.     

Cypellogins A, B and C, acylated flavonol glycosides from Eucalyptus cypellocarpa

Three new acylated flavonol glycosides, cypellogins A (1), B (2) and C (3), along with eight known phenolic compounds, were isolated from the dried leaves of Eucalyptus cypellocarpa, and their structures were elucidated using spectroscopic methods, including 2D NMR experiments and chemical evidence.     

Electroactive supramolecular self-assembled fibers comprised of doped tetrathiafulvalene-based gelators

New electroactive supramolecular fibers have been formed by self-assembly of the derivatives of tetrathiafulvalene (TTF) in liquid crystals. These derivatives are designed and prepared by introducing the TTF moiety to the scaffold derived from amino acids such as L-isoleucine whose derivatives function as organogelators. These TTF-based gelators form stable fibrous aggregates in liquid crystals. These fibers are the first example of hydrogen-bonded one-dimensional aggregates having electroactive moieties whose electrical conductivities were measured after doping. Their electronic states have also been characterized by spectroscopic methods. Unidirectionally aligned fibers are formed in the oriented liquid crystal solvents on the rubbed polyimide surface for further functionalization of the fibers.     

Azeotropic-like (congruent melting) phenomena of lamellar liquid crystals

The binary system of water and didecyldimethylammonium bromide (DDeAB), having a double hydrocarbon chain, was found to exhibit exhibit an azeotropic-like phase transition from lamellar liquid crystal to micellar solution. That is, the maximum limiting value of temperatures where the present system is allowed to exist in a lamellar liquid crystal corresponds to the socalled azeotropic point (AZP) or congruent melting point. At this temperature, the compositions of the liquid crystal and micellar solution phases become identical. Upon addition of a small amount of NaBr, the AZP shifts to a high temperature, but the point disappears above 0.375 wt% NaBr in water. The AZP is also increased by adding cholesterol. On the other hand, the transition enthalpies at AZPs are extremely small and almost constant, even if NaBr and cholesterol are added. The sharp DSC peak is observed in the presence of salt, whereas it is broad in the presence of cholesterol. It is considered that salt induces a closely packed state of the liquid crystal phase. Although cholesterol also has an ordering effect on the surfactant aggregates its hydrophobic property increases the phase transition temperature. The phase transition occurs due to a packing change of the hydrocarbon chains of DDeAB molecule from the lamellar to micellar states. The correlation between the movement of AZP and the phase behavior in the presence of salt is also discussed.     

Spectroscopic and optical characterization of porphyrin chromophores incorporated into ultrathin polyimide films

Polyamic acid (PAA) containing free-base porphyrin and zinc(II) porphyrin chromophores was synthesized by copolymerization of diphenylether-type tetracarboxylic dianhydride and diamines. The monolayer of the alkylamine salts of PAA (PAASs) at the air/water interface was deposited on solid substrates by the Langmuir-Blodgett (LB) technique. The PAAS LB films thus obtained were converted to polyimide (PI) LB films by chemical treatment. The fluorescence of porphyrin moieties in the PI LB film was observed, because of the weak electron-accepting properties of the diphenylether unit. Therefore, the photophysically important processes, such as photoinduced electron transfer, excitation energy transfer, and excitation energy migration could be investigated in relation to the layered nanostructures of the ultrathin PI films. The fluorescence spectrum suggested that the aggregation of porphyrin moieties in the PI LB films was effectively prevented by the use of polymeric films. The surface plasmon (SP) measurement showed that the thickness of the monolayers was 0.9-1.0 nm for PAAS films and 0.32-0.40 nm on average for PI LB films. The absorption dichroism of the Soret band of porphyrin indicated that porphyrin moieties in the PAAS and PI LB films are oriented in parallel with the substrate. These results showed that the orientation and the spatial distribution of porphyrin units can be efficiently regulated in the PI LB films in a nanometer dimension.     

Reaction of azulenes with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate (TPT) and synthesis of the parent azulene

2-Azulenyl trifluoromethanesulfonate was prepared by the reaction of 2-hydroxyazulene with trifluoromethanesulfonic anhydride in the presence of triethylamine as a base. Under the use of pyridine, 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate further reacted with 2-azulenyl trifluoromethanesulfonate to give 1-(1-trifluoromethanesulfonyl-1,4-dihydropyridin-4-yl)azulenyl trifluoromethanesulfonate. Moreover, we found that azulenes also reacted with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate to give 4-(1-azulenyl)-1,4-dihydropyridine derivatives and 6-(1-azulenyl)-1-trifluoromethanesulfonyl-1-aza-hexa-1,3,5-triene depending on the reaction conditions. 2-Azulenyl trifluoromethanesulfonate was converted finally into the parent azulene in excellent yield by palladium-catalyzed reduction using formic acid as a reducing reagent.     

Preparation and examination of calcium ion-selective electrodes for flow analysis

The preparation of calcium ion-selective electrodes based on known alkylphenylphosphate exchangers or on the ETH 1001 ionophore, and their use in a flow-through cell in a flow-injection system for the determination of calcium are described. The response and lifetime of the electrodes and the effects of magnesium and sodium ions on the determination of 10^?3?10^?5 M calcium are examined in detail. The ionophore electrode is shown to be most satisfactory.